In recent years, as the light-emission efficiency of the semiconductor light-emitting element such as the LED element has improved, the application thereof to the light source for lighting or the like has progressed at rapid pace.
FIGS. 13 to 15 show one example of the light-emitting source in which the LED element is used.
A light-emitting source 101, as shown in FIG. 13, is provided with an LED element 105 implemented, as the light source, on a main surface of a substrate 103. The LED element 105 is sealed with resin that includes a phosphor material in the state where the LED element 105 is disposed in a reflection hole of a reflection plate 107. Note that the resin used to seal the LED element 105 is called a sealing resin member 109. A circumferential surface constituting a reflection surface 107a reflects the light coming from the LED element 105 so that it travels in a predetermined direction (see Patent Document 1 identified below).
With the above-described structure, the light emitted from the LED element 105 is converted into a desired color by the phosphor material contained in the sealing resin member 109 as the light passes through the sealing resin member 109, and then either directly emitted from the light-emitting source 101 or reflected by the reflection surface 107a to travel in a predetermined direction and then emitted from the light-emitting source 101.
As the material of the sealing resin member 109 provided in the light-emitting source 101, epoxy resin, olefin resin or the like has been used conventionally. However, there is a problem with these resins that, when such a resin is used for a long time, the color of the sealing resin member 109 changes due to, for example, the heat that is generated as the LED element 105 emits light, resulting in reduction of the amount of light emitted from the light-emitting source 101.
A typical trend in solving the above-described problem in recent years is that, as shown in FIG. 14 or 15, a resin that does not include a phosphor material is used as the resin for sealing the LED element 105 (this resin is also sealing resin member and is represented by reference numbers 113 and 123), and that a resin including a phosphor material (this resin is called phosphor layer and is represented by reference numbers 115 and 125) is also used independently of the sealing, resin members 113 and 123, where a gel-like or rubber-like resin such as a silicone resin is used as the phosphor layers 115 and 125 (see Patent Document 2 identified below).
It should also be noted here that the phosphor layers 115 and 125 may be made respectively in the shape of a plate with substantially constant thickness and in the shape of a dome, as shown in FIGS. 14 and 15, so that the light path lengths (examples of which are L3 and L4 shown in FIG. 14) of the light passing through the phosphor layer after passing through the sealing resin member 113 or 123 can be equalized, preventing an occurrence of color unevenness.    Patent Citation 1: Japanese Patent Application Publication No. 2005-311170    Patent Citation 2: Japanese Patent Application Publication No. 2005-166733